In recent years, as means for synthesizing a substance for preventing thrombogenesis, a method which comprises causing the activated blood coagulation factor which is a serine protease to react with such an inhibitor as phenylmethylsulfonyl fluoride (PMSF) thereby converting active site serine into dehydroalanine and consequently eliminating the serine protease activity but retaining the binding ability with thrombin substrates (designated as “anhydridization”) disclosed in the official gazette of JP-A-11-49800 and a method which eliminates the serine protease activity by the manipulation of gene recombination have been developed. The anhydrothrombin which is obtained by treating thrombin by the use of such a method inhibits interactions between activated blood coagulation factors and substrates competitively, and is expected to be utilized as a ligand for an adsorbent of thrombin substrates (such as, for example, an activated blood coagulation factor and fibrinogen) and as an inhibitor against thrombogenesis.
However, since serine protease activity of anhydrothrombin was eliminated by only the chemical treatment or the manipulation of gene recombination and its fundamental binding ability with substrates is not different from untreated thrombin, it has been difficult to absorb and to recover blood coagulation factor VIII selectively from such a liquid as plasma, which is a mixture of several thrombin substrates (such as blood coagulation factors V, VIII, XI, and XIII, fibrinogen, and Protein C). Further, the anhydrothrombin has found only limited utility because it is required to be used in an unduly large amount for the purpose of showing the same antithrombogenetic effect as the antithrombotic agent as mentioned above, though it indeed can function as an antithrombotic agent.
In diagnosis of abnormality of platelet functions, determination of ability of platelet aggregation is an essential requirement and thrombin is used for the determination as a substance that induces platelet aggregation. However, since thrombin activates fibrinogen as well as induces platelet aggregation, it has been a problem that fibrin clot exerts an adverse effect on the determination of the ability of platelet aggregation.
Concerning the thrombin which constitutes an activated blood coagulation factor or the anhydrothrombin which results from anhydridizing the thrombin, this invention has an object of providing a thrombin or anhydrothrombin derivative having an improved selectivity thereof for a thrombin substrate (blood coagulation factor VIII) by the modification using a chemical or genetic manipulation, a substance for inducing aggregation of blood platelets and a clinical testing agent containing the thrombin derivative as a component, an adsorbent using the anhydrothrombin as a ligand, and an antithrombotic agent having an improved antithrombotic ability thereof constituting the anhydrothrombin derivative as a main component.